The original version of this paper
was first presented in Project Management World Today in the March 2000 issue.
It was subsequently updated and reproduced on this web site in November 2000.
This is Revision 17, March 2009.

Discussion - Tetrad Trade-off Principle

Issue #8: Although the term "Tetrad Trade-off" has been in the literature
for some years,[30] objection has been
raised because the term is unfamiliar.

Perhaps this is the very value of the term - to emphasize that there are four separate but interactive variables (scope, quality, time and cost) rather than just three as in the old and obsolete view of Triple Constraint (time, cost and performance.) Thus, quality, the most enduring variable of the four when it comes to project success, is given new prominence. It should be stressed here again that quality means Quality Grade, i.e. the measure of level or class (utility to world-class) as distinct from Quality Conformance, i.e. "conformance to specified requirements".

Interestingly, the "dimensions of the Tetrad" are affected by the skills and experience, i.e. the expertise and hence efficiency, of the team doing the work. The more "expertise" the team has, the higher their situational awareness and the faster their "learn-rate". In addition they can typically perform tasks faster because of their prior learning. These capabilities allow teams of experts to achieve more with less. This ability expands what can be achieved and hence affects the size and shape of the Tetrad. This point is often lost on managers who see resources as fully interchangeable and homogeneous.

Acknowledgements

I am indebted to the many people who have contributed to this discussion. In particular I should like to thank Bill Duncan, Project Management Partners; Chris Quaife, Symmetric Resources; Eric Jenett, FPMI; and Robert Goatham, Calleam Consulting; for their extensive, very valuable and insightful comments.